This project is aimed at enhancing the maintenance of weight losses achieved through the use of the very-low-calorie diet (VLCD) in persons with moderate to severe obesity, a degree of obesity that carries with it increased rates of morbidity and mortality. The project is also aimed at increasing our knowledge of the factors associated with poor maintenance of weight loss in this group of individuals. The effectiveness of a new method of reintroducing food following the VLCD fast will be examined. This method is designed to gradually reintroduce the full range of stimuli associated with the consumption of food, making use of findings from basic research concerning the phenomenon of sensory specific satiety. 200 moderate to severely obese individuals will participate in a VLCD fast combined with behavior therapy, allowing for dropouts in order to enter 160 individuals into the experimental phase of this study. These individuals will be allocated at random to one of four groups: 1. Standard treatment, time-dependent reintroduction of regular food. 2. Time dependent introduction of prepackaged food of limited variety. 3. Individual reintroduction of regular food dependent upon weight maintenance. 4. Individuals reintroduction of prepackaged food dependent upon weight maintenance. Recommended caloric intake and instruction in behavior changes relevant to weight maintenance will be identical for each of these groups. Participants will be followed for 18-months following completion of the "CD phase with measures of adiposity, eating behavior, activity levels, and psychosocial variables relevant to obesity. This design will also allow the influence of variables suspected to affect maintenance to be examined prospectively. Such variables include: family history of obesity; response to and compliance with initial treatment; predisposition to binge eating; depressed/anxious mood; negative mood associated with eating; stressful life events; inadequate social support; and level of self- efficacy to carry out elements of the treatment program.